This invention relates to a blood collecting tube for collecting a blood sample for use in various blood tests.
Various blood collectors have been in clinical laboratory tests such as biochemical examinations and serologic tests. Generally used blood collectors are of the type comprising a blood collecting tube whose interior is kept under reduced pressure, and a tube holder capable of receiving the blood collecting tube therein and provided with a puncture needle at the tip thereof. The blood collecting tube comprises a tubular member made of glass or synthetic resin which has an open end and a closed bottom, and a rubber plug for closing the open end of the tubular member.
A tubular member made of glass can maintain the reduced internal pressure thereof for a long time but it is easily damaged in transportation and operation. The resultant damaged tubular member causes the contamination of the blood sample in the tubular member. Additionally, a glass tubular member is relatively heavy to handle. In contrast to this, a plastic tubular member made of synthetic resin is advantageous because it is light and difficult to damage even when dropped.
A blood collecting tube using a conventional plastic tubular member has, however, the problem that the capability of collecting blood considerably decreases with time because of the insufficient gas-barrier properties of the tubular member. Although there is known a plastic tubular member made of polyethylene terephthalate, it is also disadvantageous because polyethylene terephthalate is easily whitens at the gate position upon injection molding and clogs the gate of the injection molding machine. It results in low productability.